Heat exchange unit



y 1944. w. E. MCCULLOUGH 2,347,957

HEAT EXCHANGE UNIT Filed June 17, 1939 3 Sheets-Sheet 1 INVENTOR. W/Y/lb/fl 5 Me Cu//ouy ATTORNEY.

y 1944- I w. E. MCCULLOUGH 2,347,957

HEAT EXCHANGE UNIT Filed June 17, 1939 3 Sheets-Sheet 2 y 2, 1944- w. E. MccuLLouel-l 2,347,957

HEAT EXCHANGE UNIT Filed June 1'7, 1939 3 Sheets-Sheet 5 all 4 INVENTOR. W/Y/l'd/M '5 Me Cu//o (19% Patented May 2, 1944 UNEHED STATES PATENT OFFICE HEAT EXCHANGE UNIT William E. McCullough, Detroit, Mich. Application June 17, 1939, Serial No. 279,617 6 Claims. (01257-149) This invention relates to a heat exchange deefficient unit that can be adapted to a wide variety of installations.

Important features of the invention reside in the fact that the unit is formed from a single continuous length of extruded stock that can be subjected to some of the fabricating operations in mill lengths, and that in the finished unit the parts are disposed so as to make efiicient use of air currents flowing transversely of the unit.

Another important feature of the invention resides in the fact that the tube section is extruded with straight lateral fins homogeneous therewith and that these fins are subsequently bent. beyond the width of the tube'section, preferably by being crimped or ruflled.

The fins areremoved from portions of the tube to prepare the ends for attachment to other tubing, and from intermediate portions to facilitate bending.

While preferred forms of the apparatus and method are disclosed herein for purposes of illus I tration, various changes may be made therein without departing from the spirit of the invention as herein set forth and claimed.

In the drawings:-

Fig. 1 is a side elevation of a heat exchange unit embodying the invention.

Fig. 2 is a view partly in section and partly in elevation, taken on line 2-2 of Fig. 1.

Fig. 3 is a perspective of one form of stock as extruded.

Fig. 4 is a perspective showing the stock after the tube section has been flattened.

Fig. 5 is a perspective showing the stock after the fins have been ruffed.

Fig. 6 is a plan view of a length of stock after parts of the fins have been removed.

Fig. 7 is a perspective illustrating the bends in the finished unit.

Fig.8 is a perspective of one end of the stock after the tube section has been prepared for attachment to other tubing. I

Fig. 9 is a fragmentary side elevation illustrating a modification.

Fig. 10 is a view similar'to Fig. 3 showing a modified form of extruded tubing.

Fig. l1 is a side elevation modification.

Fig. 12 is a perspective of a modified form of tubing stock as extruded.

Fig. 13 is a side elevation illustrating an additional modification. i

illustrating a further I II, and the ruiiies part of one of the line l6-I6 of Fig. 15. Referring to the drawings more particularly,

Fig. 1 shows as a preferred form of the invention a heat exchange unit adapted for use as a condenser for a mechanical refrigerator. As clearly shown in this figure, the main part of the unit is a continuous length of tubing stock Ill. The details of the structure shown in Fig. i: will be understood best by following the operations by which the tubing stock is given its final form.

This tubing stock is preferably extruded from aluminum alloy, which is asuitable material because it has a high coemcient of heat conductivity; lends itself readily to extrusion and to the other operations of manufacture; and resists corrosion by the ordinary refrigeration fluids. Other materials having desirable properties could of course be used for the tubing stock.

The tubing stock is extruded, as illustrated in Fig. 3, 'with a central tube section H and thin lateral fins l2. The central tube section originally has the shape of an oval with the major axis of the oval lying in the plane of the fins l2, this shape being used because it approximates-the flattened shape desired in the finishediunit. The tubing stock illustrated can be continuously extruded in any convenient mill lengths.

In the next operation the tubing stock is run through rolls, or other suitable apparatus, by which the central tube section is flattened to a V fiat-sided tube as illustrated in Fig. 4. This final shape is preferred because it lends itself readily to forming the close bends required in the unit, and because it provides a minimum depth of tube with a thin fluid column that is efficient for heat transfer. If desired, the flattening may be done only at the parts to be bent, leaving the other parts in the shape as originallyextruded.

Either subsequently to, or simultaneous with the flattening operation, the edges of the fins I! are crimped or ruiiied by rolling or stamping, so that in the finished unit the part of each fin attached to the tube section II is straight, while its free edge has a sinuous curve or rufile, as clearly shown in Fig. 5. The ruiiling is sufficiently deep that the crest I3 of each crimp or ruflie lies beyond the normal width of the tube section on both sides of the strip are crest of one ruflle is the same end of the tube as the crest alined, that is, the distance from the of the male on the other side of the tube. This milling has several advantages, some of which are that it increases the area of the fins while reducing their thickness, heat-transfer capacity of the fins, and that it makes emcient contact with air currents flowing across the tube section.

In the next operation the tubing stock is subjected to a stamping operation by which part of each fin I2 is cut off at ll, adjacent each end of the piece of stock, and at I, points corresponding to the bends of Fig. 1. This stamping operation may press'or by suitable cutting rolls.

. The length of tubing stock is then ready tobe bent. During the bending precautions must be taken to prevent collapse of the tube section II at the bends. and this is conveniently done by drawing into the tube a flexible supporting element having ashape corresponding with the inner contour of the tube section and preferably built up from pieces of flexibleshim stock. The

flexible support is drawn to a position inside one of the de-flnned sections l5 and that section is then bent into a flat U bend as illustrated in Fig. 7. The flexible support is then drawn on to the next bend.

Succeeding bends are made in opposite directions, so that in the finished unit the straight runs between bends are disposed vertically above each other and are spaced from each other a suflicient distance to prevent the crests II of the ruiiles ofone run from contacting with the crests of the ruiiies of the adjacent run. When all bends have been made the flexible support is removed from the tube section.

After the length of stock has been bent as described each end of the tube section I l is suitably formed for attachment to the tubes of a system, such as a refrigeration system.. In the embodiment illustrated the tube section II is expanded into tubular shape as at l6 and its end is upset to form v a thickened collar as at I! in Fig. 8. These prepared ends may conveniently be welded to the copper tubes of the refrigeration system in a. known manner.

After the unit formed from the extruded stock has been thus shaped it is preferably mounted in a supporting frame. The frame shown in Fig. 1 comprises a base plate II and side members is. The side members l9 have openings 20 which have a snug fit over the bends I! of the tube section. Tie rods 2| hold the side members I! firmly against the tube section.

v The condenser unit described above is intended for use with a fan blowing a current of air across the unit to cool and condense warm refrigeration fiuids flowing through the tube section Ii.

The fan would normally be located behind or,

in front of the unit as positioned in Fig 1 and the air current would flow across, that is' at right angles to, the tube section II.

This construction has a number of advantages. In the first place it consists basically of a single length of tubing having fins homogeneous with the tube. Since a joint of any kind impedes heat flow, the homogeneous construction provides for the most eflicient heat transfer from the tube to the fins.

As previously stated, the ruiiiing of the fins increases the fin area while decreasing the thickness' of the fins, thus enhancing the heat transfer capacity of the fins. At the same time the ruiiles help to make efllcient use of the air stream thus enhancing the be carried out by a stamping flowing across the unit in the manner now to be explained. i

In Figs. 7 and reference numerals 22 and 23 represent ruffles located on adjacent runs of the 5 tube section, the crests of these rumes extending away from each other and beyond the width of the tube section II. Due to this construction each of these ruifles acts as an air scoop, and between them is an opening having a genlo eral funnel shape which narrows down to a fiat opening 24 between the runs of tube section, and which flares out again in a corresponding funnel shaped opening defined by the matching ruffles I! and 28 on the rear side of the runs of 15 section II. The cross-section through these ruffles (Fig. 16) shows that the air stream first impinges forcefully against the fins 22 and 23, then rushes with increased velocity through the 1 Venturl -tl'iroat ,24, and expands to make contact with the ruilles and 20.

It will be clear from Fig. 1 that similar Venturi throats extend over both sides of each interior run of the tubing stock, so that the construction provides for an accelerated flow of air 25 over both sides of the tube section H, as well as for direct impingement or positive wiping action of the air upon the fins.

Persons skilled in the art will understand that the construction above described is not limited so to use as a refrigeration condenser unit, but

that it can be used wherever -a simple, inexpensive heat-exchange device is 'required. It may, of course, be mounted with the straight runs extending vertically, and many variations as can be made in the construction some ofwhieh will now be described.

Fig. 9 shows a modification on which a unit is built up basically like that illustrated in Fig. 1, but with the differences that in Fig. 9 the parallel runs of the tubing stock are spaced closer together so that the projecting rufiies of adjacent runs contact with each other. In this form the ruflles provide venturial openings that are completely closed at their outer ends. However, in 5 this construction the touching ruflles should be prevented from rattling by fastening them together with. rivets, clips, welding, soldering or brazing. Y

The tube stock may, of course, be extruded with any preferred form of central tube section. For example, Fig. 10 illustrates a shape of extruded stock in which the tube section 21 is cylindrical and this section may be left in this shape in the finished. condenser unit, or it may be flattened as previously indicated in Fig. 4.

For some installations it may be desirable to pass a larger amount of fluid through the heat exchanger relative to the amount of fin area. One construction for obtaining this result is 00 illustrated in Fig. 11 in which two units of the general type illustrated in Fig. 1 are nested together. One of these units, indicated by reference numeral 20, has relatively wide bends 29 at the left side of Fig. 11 and relatively sharp bends III at the right end of Fig. 11. The other unit, indicated by the numeral 3i, has relatively sharp'bends 32 at the -left end of Fig. 11 and relatively wide bends 33 at the right end. Nesting these units together they may be brought to the position illustrated in Fig. 11 in which the ruillesof the units are aligned. The ruiiles may touch each other as illustrated in Fig. 11, or may be spaced apart in the manner' indicated in Fig. 1.

.The inlet leads of the units 2! and II are this construction the fin areais the same as for a similar unit having the same number and length of straight tubing runs. but since there are two separate tube sections ll running through the unit, twice the amount of fluid will pass through the tubes oi the unit as would pass through a single tube unit 01' the same size.

Another construction to obtain an increased fluid fiow is illustrated in Fig. 12 in which the tubing stock is extruded in the form of a fiat strip having a plurality of tube sections ll joinedby fin l2 and having laterally extending fins l2. In the io'rm illustrated having two tubes [j the fluid capacity of the section is doubled while the fin area is increased 50%. The outside fins I2 may, of course, be rufiled in the manner heretofore explained, and the central fin may also be criniped to increase its area" and to take advantage oi the air flow. More than two tubes may, oicourse, be extruded on a single piece of stock ii desired.

Another possible variation of the construction is illustrated in Fig. 13 in which the laterally extended flanges are not crimped but the entire fin is tilted toa position in which it projects beyond the width of the tube section II into the 7 air stream between adjacent runs of the tubing stock. Thus the front fin 36 of each run may be bent downwardly and the rear fin 31 may be bent upwardly as indicated'clearly in Fig. 14. This form of the device would not make as efiicient contact with the air stream as the forms having the milled fins, but it may be satisfactory for some purposes. This construction with straight tilted fins may be used in a nested,unit of the kind shown in Fig. 11.

-I claim: j

1. A heat exchange unit comprising a. single length of extruded aluminum stock having a central flattened seamless tube section and two lateral fins thinner than the tube section and homogeneous therewith and extending from opposite sides of the tube section, the length of stock being bent into successive runs spaced from each other to form a unit adapted for air flow transverse to the ms, the outer edge of each fin being at the bends, and the ends of the-,stock having the lateral'fins removed.

2. A heat exchange unit as set forth in claim- 1 in which the ruiiles of adjacent runs touch each other and are joined together by brazing or soldering.

3. A heat exchange unit as set forth in claim 6 in which two separate lengths of tubing are bent and nesimd together in the same plane t'o provide a plurality of fiuid passages through the unit.

4. In a heat exchange unit of the type in which two runs of tubing stock-are located adjacent to each other, the improvement which comprises:

each run 01' tubing stock having two finsthat extend at right angles -to the plane passing through the centers of the tubing stock, each of the fins having its outer edge ruffled, the crests of the rufiies extending beyond the width of the tubing stock and being alined with the crests of rufiled, the crests of the ruifles of adjacent runs being alined with each other and having their crests extending beyond the width of the tube section in a direction transverse to the normal line of the fin, parts of the stock being formed into simple bends, the lateral fins being removed the ruiiles of the fins of the adjacent run so as to form Venturi-like openings, the tube portions of the tubing stock forming side walls of the Venturi throats.

5. A heat exchange-unit comprising a section 01' stock having a seamless tube-part and two lateral fins thinner then the tube part, homogeneous therewith and extending from opposite sides of the tube section, both of the lateral fins having their outer edges rufiled, the crests of the miles extending beyond the width of the tube in adirectiontransverse to the normal line of the fin, the crests of the ruiiies of one fin being alined with those of the other fin, the section of stock being placed adjacent to another section of similar construction, the crests of the rullies of the adjacent sections being alined with each other so as to form Venturi-like openings, the tube sections forming the sides of the Venturi throats.

6. In a heat exchange unit 01' the type in which two runs of tubing stock are locatedadjacent to each other, the improvement which comprises":

the tubing stock being a seamless section of ex-' truded metal having oppositelyextending fins. homogeneous with the tubing and attached to the v tubing along continuous, straight lines parallel with the axis of the tubing, each of the-fins being formed with ruflies which commence adjacent the straight edge where thefin is attached to the tube and increase in depth-toward the outer sinuous edge of the fin, the crests of the ruffles of one fin of a run being alined with the crests of the other 

